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April 18, 2014

Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

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Chemistry
so for all the chemical formulas if there is no subscript (for the valency of the element) does it mean it is a one or do i have to find the valency on the periodic table of elements? ex. P02 the P for Phosphorus doesn't have a number does it mean it is a one then ex.SO3 ...
Sunday, February 16, 2014 at 7:43pm

Chemistry
where is the -678 coming from?
Sunday, February 16, 2014 at 7:26pm

AP Chemistry
The rate of effusion of unknown gas X is found to be about 1.5 times that of SF6 gas (MW=146 g/mol) at the same conditions of temperature and pressure. What is the molecular weight of gas X? Answer in units of g/mol
Sunday, February 16, 2014 at 7:03pm

AP Chemistry
A 1277 mL sample of nitrogen (N2) was collected by displacement of water at 24 degrees C under a total barometric pressure of 966 torr. What mass of dry nitrogen was collected? The vapor pressure of water at 24 degrees C is 22 torr. Answer in units of g
Sunday, February 16, 2014 at 7:03pm

AP Chemistry
Part 1 of 3: An apparatus consists of a 2 L flask containing nitrogen gas at 30 degrees C and 758 kPa, joined by a valve to a 11 L flask containing argon gas at 30 degrees C and 49.7 kPa. The valve is opened and the gases mix. What is the partial pressure of nitrogen after ...
Sunday, February 16, 2014 at 7:01pm

AP Chemistry
We drop 30 grams of magnesium into 770 mL of a 4 M HCl solution. What is the maximum volume of dry hydrogen that could be produced by this reaction at STP? Mg(s) + 2HCl(aq)→MgCl2(aq) + H2(g) Answer in units of liters
Sunday, February 16, 2014 at 6:59pm

AP Chemistry
Iron pyrite (FeS2) is the form in which much of the sulfur exists in coal. In the combustion of coal, oxygen reacts with iron pyrite to produce iron(III) oxide and sulfur dioxide, which is a major source of air pollution and a substantial contributor to acid rain. What mass of...
Sunday, February 16, 2014 at 6:56pm

AP Chemistry
We observe that 5 grams of a gaseous com- pound occupies 2083 mL at 50 degrees C and 574 torr. What is the molecular weight of the compound? Answer in units of g/mol
Sunday, February 16, 2014 at 6:54pm

AP Chemistry
A 2.8 gram sample of a gaseous substance occupies 12 L at 47 degrees C and 683 torr. What is the density of the gas under these conditions? Answer in units of g/L
Sunday, February 16, 2014 at 6:54pm

AP Chemistry
What pressure would a mixture of 3.2 grams of O2, 6.4 grams CH4, and 6.4 grams of SO2 exert if the gases were placed in a 4.1 liter container at 127 degrees C? Answer in units of atm
Sunday, February 16, 2014 at 6:53pm

AP Chemistry
Nitroglycerin is a shock-sensitive liquid that detonates by the reaction 4C3H5(NO3)3(ℓ)-> 6N2(g)+10H2O(g)+12CO2(g)+O2(g) Calculate the total volume of product gases at 201 kPa and 273 degrees C from the detonation of 3.3 lb (1496.9 g) of nitroglycerin. Answer in units...
Sunday, February 16, 2014 at 6:51pm

AP Chemistry
To what temperature must a sample of helium gas be cooled from 110 degrees C to reduce its volume from 4.9 L to 0.7 L at constant pressure? Answer in units of K
Sunday, February 16, 2014 at 6:49pm

Chemistry
Carbon monoxide and chlorine gas react to form phosgene: CO(g)+Cl2(g)⇌COCl2(g) Kp = 3.10 at 700 K If a reaction mixture initially contains 319torr of CO and 220torr of Cl2, what is the mole fraction of COCl2 when equilibrium is reached?
Sunday, February 16, 2014 at 6:46pm

Chemistry
now I understand. thank you (:
Sunday, February 16, 2014 at 5:58pm

Chemistry
That's right. In fact that is the whole concept behind balancing redox equations. You count up the electrons lost from one side to the other; count up electrons gained from one side to the other, then multiply by whatever numbers you need to make electrons gained equal ...
Sunday, February 16, 2014 at 5:45pm

Chemistry
Zn + 2HCl ==> ZnCl2 + H2 mols Zn = 0.10 mols HCl = M x L = 1 x 0.150 = 0.150 First you must determine the limiting reagent (LR). You know this is a LR problem because amounts are given for BOTH reactants. a. Convert 0.10 mol Zn to mols H2. That's 0.10 mol Zn x (1 mol H2...
Sunday, February 16, 2014 at 5:39pm

Chemistry
thanks so much. so you would always count up the oxidation states and see how much one side needs to equal the other?
Sunday, February 16, 2014 at 5:29pm

Chemistry
It isn't a hard question if you remember that in a balanced equation the number of mols electrons lost ALWAYS equals the mols gained. There is a second but more work way of doing it like this. Oxidation state Fe on the left is 0. On the right is +6 (2*3+ = 6+) and going ...
Sunday, February 16, 2014 at 5:25pm

Chemistry
If 0.10 mol of Zn(s) is reacted to 150.0 ml of 1M HCl, what is the concentration of Zn+2 in the solution after the reaction is complete? Assume the solid zinc does not affect the volume.
Sunday, February 16, 2014 at 5:22pm

Chemistry
Given the balanced equation representing a reaction : 2Fe+ 3Cu^2+ --> 2Fe^3+ +3Cu When the iron atoms lose six moles of electrons, how many moles of electrons are gained by the copper ions? (1) 12 moles (2) 2 moles (3) 3 moles (4) 6 moles how would i even start solving a ...
Sunday, February 16, 2014 at 5:16pm

Chemistry
.0143
Sunday, February 16, 2014 at 3:45pm

chemistry
volume = 64.8-22.9 = ? mL = ? cc. Then density = mass/volume = ? g/cc or g/mL.
Sunday, February 16, 2014 at 3:38pm

chemistry
See your other post.
Sunday, February 16, 2014 at 3:37pm

chemistry
volume = length x width x height = ? cc. Then density = mass/volume = ? g/cc
Sunday, February 16, 2014 at 3:36pm

chemistry
What is the density of a 33.13 g irregularly shaped object if the initial volume of water was 22.9 ml and the volume rose to 64.8 ml after the object was added?
Sunday, February 16, 2014 at 3:05pm

chemistry
What is the density of a 19.74 g object if the dimensions of the block are: length = 12.6 mm height = 2.50 cm width = 0.0140 m
Sunday, February 16, 2014 at 3:04pm

chemistry
What is the density of a block of unknown material with a mass of 17.02 g if the dimensions are: length = 2.2 cm height = 1.7 cm width = 2.7 cm
Sunday, February 16, 2014 at 3:04pm

chemistry
ghgh
Sunday, February 16, 2014 at 3:02pm

chemistry
A volume of water delivered using a buret has a mass of 2.67 g. What was the final volume reading on the buret if the inital volume reading was 0.12 ml? [assume the density of water is 1.00g/mL]
Sunday, February 16, 2014 at 2:58pm

Chemistry
How can we help you with this assignment? One similarity is that both yield the same products. One difference is that the temperature rises rapidly in combustion but over a longer period of time for metabolism (although the heat generated is the same).
Sunday, February 16, 2014 at 2:58pm

Chemistry
If you are given a name that has a metal with a multivalent possibility, the Roman numerals will tell you which to use. For nickel(I) oxide, that tells you Ni is I (i.e., +1) and not II (i.e., +2. the other common valence). Oxygen usually is -2 so you write Ni2O. For nickel(II...
Sunday, February 16, 2014 at 2:55pm

AP Chemistry
mmols = millimols = mL x M. mmols CH3COOH = 500 x 0.1M = 50 mmols NaOH = 500 x 0.167 = 83.5 Total volume = 500 + 500 = 1000 mL ....CH3COOH + Na^+ + OH^- --> CH3COO^- + Na^+ + H2O I......50.....83.5........0........0 C.....-50.....-50........+50......+50 E......0......33.5...
Sunday, February 16, 2014 at 2:44pm

AP Chemistry
A solution is made by mixing exactly 500 mL of 0.167 M NaOH with exactly 500 mL of 0.100 M CH3COOH. Calculate the equilibrium concentrations of H+, CH3COOH, CH3COO-, OH-, and Na+.
Sunday, February 16, 2014 at 1:55pm

chemistry
12
Sunday, February 16, 2014 at 1:50pm

Chemistry
i need to write to chemical formula for sulphur(II)iodide but both are non metals what do i do and i get confused sometimes cause i don't know when the metal/non metal gets a one charge (for the valences) ex. NiO =Ni1O2 =Ni2O =Nickel(I)Oxide ex. NiF2 =Ni1F2 =Ni2F =Nickel(...
Sunday, February 16, 2014 at 1:38pm

Chemistry
Compare and contrast the combustion of sugars to biological metabolism of sugars
Sunday, February 16, 2014 at 1:37pm

Chemistry
A. is wrong that is not one of the answers. I have calculated 1.5912 X 10^-28 but the only near answer is 1.591 x 10^-19
Sunday, February 16, 2014 at 12:32pm

CHEMISTRY
See your other question.
Sunday, February 16, 2014 at 12:09pm

chemistry
You must have tables or graphs from which to obtain these data. I certainly don't have these things memorized. If you don't have this information in your text/notes, Google them and see if you can't find the numbers that way.
Sunday, February 16, 2014 at 12:08pm

chemistry
8.37g/3.1cm^2 = 2.7 g/cm^3 Looks like aluminum to me.
Sunday, February 16, 2014 at 12:07pm

chemistry
a metal object has a mass of 8.37g. when it was placed in a graduated cylinder containing 20.0ml of water, the water level rose to 23.1 ml. what is the density and identity of the metal?
Sunday, February 16, 2014 at 10:55am

CHEMISTRY
Determine the followng solutes disolved in 100 g of water will form unsaturated or saturated solution a. 180g Kl at 60DGREE CELSIUS . 60g KBr at 30 DEGREE CELCIUS c170g KNO3 at 50 dgree celcius d. 20 g NaCl at 90Degree celcius
Sunday, February 16, 2014 at 10:29am

chemistry
determine the solubility in g/100 g water of A. KNO3 at 90DEGREE CELCIUS B. KBr at 80 degrees celcius C. Kl at 0degree celcius D. KCl at 40 DEGREE CELCIUS
Sunday, February 16, 2014 at 10:27am

Chemistry
1. A student uses 6M HCl solution contaminated with Al(NO3)3 to wash the nichrome wire in between recordings of emission spectra for the different known and unknown metal ion solutions. The emission energies for the aluminum are 3.90x10^-19 J/atom, 3.58x10^-19 J/atom, and 2....
Sunday, February 16, 2014 at 4:00am

Chemistry
40% is 40 g sucrose/100 g solution. Use density to convert 100 g solution to volume in cc and convert that to L. Convert 40 g sucrose to mols. mol = grams/molar mass. Then M = mols/L
Sunday, February 16, 2014 at 1:59am

Chemistry
At 25 °C, the density of a 40.0% (m/m) solution of sucrose, C12H22O11, in water is 1.18 g/mL. What is the molarity of this solution?
Sunday, February 16, 2014 at 1:12am

Chemistry
A. E/photon = hc/wavelength. wavelength = 1.350E-9 m B. I obtained 40.08 using 6.022E23 for Avogadro's number. C. looks ok to me. D. c = freq x wavelgnth
Saturday, February 15, 2014 at 10:53pm

Chemistry
1) Calculate the energy. in joules, of a photon of wavelength 1.250x 10^3 nm 2) If 3.011x 10^23 molecules have a mass of 20.04 grams, what is the molar mass of the substance? Is it 40.07g/mol? 3) 47.5g of Boron contains __________ atoms of B? Is it 2.65x10^24 4) What is the ...
Saturday, February 15, 2014 at 10:26pm

Chemistry
(P1V1/T1) = (P2V2/T2)
Saturday, February 15, 2014 at 10:19pm

Chemistry
A piston is holding 125 mL of gases at a temperature of 300 K and a pressure of 2.39 atm. What is the volume of the gases if the temperature is increased to 500K and the pressure falls to 2.15 atm?
Saturday, February 15, 2014 at 10:11pm

chemistry
What is the question? The empirical formula? Convert 4.23g CO2 to g C and convert that to %C. Here is how you do that. 4.23g CO2 x (atomic mass C/molar mass CO2) = 4.23 X 12/44 = about 1.15g C, then %C = 1.15/mass sample)*100 = about 45.8%C For g H it is 1.01g H2O x (2*1/18...
Saturday, February 15, 2014 at 10:09pm

chemistry
a 2.52-g sample of a compound containing only carbon, hydrogen, nitrogen, oxygen, and sulfur was burned in excess O to yield 4.23 g of CO2 and 1.01 g of H2O as the only carbon and hydrogen containing products respectively. Another sample of the same compound, of mass 4.14 g, ...
Saturday, February 15, 2014 at 9:24pm

Chemistry
So (650)(25)/248=353(x)/298 65.5241=.8441/(x) 55.3=x got it right thanks Dr.Bob
Saturday, February 15, 2014 at 8:33pm

Chemistry 106 ch 11
q1 = heat released when steam @ 122 moves to 100. q1 = mass steam x sp h steam x (Tfinal-Tinital) q2 = heat released when steam condenses. q2 = mass steam x heat vap q3 = heat released when H2O @ 100 moves to 39 C. q3 = mass H2O x sp h H2O x (Tfinal-Tinitial) Then add q1 + q2...
Saturday, February 15, 2014 at 8:13pm

Chemistry
This is (P1V1/T1) = (P2V2/T2) The must be in kelvin. What else is there to show? Substitute the numbers form the problem and solve for the only unknown.
Saturday, February 15, 2014 at 8:10pm

Chemistry
If a sample of gas occupies 25.0 mL at -25°C and 650 mmHg, what is the volume at 25°C and 353 mmHg? (Could you please show me step by step?)
Saturday, February 15, 2014 at 7:41pm

Chemistry 106 ch 11
Calculate the heat released when 73.5 g of steam at 122.0 C is converted to water at 39.0C. Assume that the specific heat of water is 4.184 J/g C, the specific heat of steam is 1.99 J/g C, and change in heat vap =40.79 kJ/mol for water.
Saturday, February 15, 2014 at 6:23pm

analytical chemistry
mols = M x L = ? mols = grams/ molar mass. Solve for grams.
Saturday, February 15, 2014 at 6:12pm

analytical chemistry
How many moles do you want? That's M x L = mols. How many grams is that? That's mols = grams/molar mass. Calculate grams. Weigh the grams, add to the 200 mL volumetric flask, add some water, swish to dissolve the solid, make to the mark with distilled water and mix ...
Saturday, February 15, 2014 at 6:11pm

analytical chemistry
You are asked to make a 0.3M CaCl2 solution in a flask that can hold 200 ml. How would you do it?
Saturday, February 15, 2014 at 3:59pm

analytical chemistry
How much NaOH (in grams) would there be in 0.25 litre of a 0.3M solution?
Saturday, February 15, 2014 at 3:58pm

Chemistry
1
Saturday, February 15, 2014 at 3:41pm

Chemistry
yes
Saturday, February 15, 2014 at 2:05pm

Chemistry
Also, if it says that the experiment was performed at 273 K, would that be the value of T in the second equation?
Saturday, February 15, 2014 at 1:40pm

Chemistry
would i=1 and delta t=.5 deg C?
Saturday, February 15, 2014 at 1:32pm

chemistry
When you've made a typo and typed 9 instead of 8. :-)
Saturday, February 15, 2014 at 12:42pm

chemistry
The smaller melting range is the higher purity. That's because of colligative properties (the decrease in melting point with added impurity)
Saturday, February 15, 2014 at 12:41pm

Chemistry
See this. http://www.jiskha.com/display.cgi?id=139​2408518
Saturday, February 15, 2014 at 12:38pm

Chemistry
Use delta T = i*Kf*m and calculate m. Then use pi = i*mRT and solve for pi
Saturday, February 15, 2014 at 12:36pm

Chemistry
Sorry, ignore that last question, I was confusing myself. But I'm still a bit confused on the process. For the XH20 of the .1 M, wouldn't the answer to that be .998 and not .0082? Even if it changes, it still doesn't change the rest of the solution, right, since ...
Saturday, February 15, 2014 at 12:27pm

Chemistry
An aqueous salt solution has a freezing point of -.5 degrees Celsius and causes neither swelling or shriveling of cells. The kf of water is 1.86 K kg/mol. What is the osmotic pressure that is exerted on cells when placed in pure water? (ignore differences between molarity and ...
Saturday, February 15, 2014 at 11:43am

Chemistry
So does that mean that at the very end, all of the solution will be in Beaker 1 and none of the solution will be in Beaker 2?
Saturday, February 15, 2014 at 11:08am

Chemistry
How would you calculate how much MgO was produced? Would you just use the first reaction 2Mg+O2 --> 2MgO or would you have to put the amount of Mg through the other reactions with the mole to mole ratios and then find the amount of MgO produced?
Saturday, February 15, 2014 at 10:52am

Chemistry
Assume that some of the magnesium nitride is not completely converted to magnesium hydroxide and subsequently to magnesium oxide. Will your empirical formula be too high in magnesium or too high in oxygen? Please show any calculations you used to determine your answer.
Saturday, February 15, 2014 at 10:08am

chemistry
you have two sample of mannitol .one melted between 168-169 c and the other melted between 161-168 .which sample has the greater purity? why?
Saturday, February 15, 2014 at 6:24am

chemistry
when does 4+4=9
Saturday, February 15, 2014 at 12:10am

chemistry
thank you
Friday, February 14, 2014 at 11:51pm

chemistry
mass % = [(mass solute)/mass solution)]*100 = ? mass solute = 7.084g mass solution = 7.084g + 123.0g = ?
Friday, February 14, 2014 at 11:37pm

chemistry
A solution is made by dissolving 7.084 g of aluminum nitrate, Al(NO3)3, in 123.0 g of water. What is the mass percentage of solute in this solution? this feels like a simple problem but i just don't know. divide the two?
Friday, February 14, 2014 at 11:09pm

Chemistry
The K is just the equilibrium constant, not Kp. Do you have to convert the K to Kp?
Friday, February 14, 2014 at 10:59pm

Chemistry
First is what happens. 1L H2O = 1000g/18.015 = 55.5 mol So in 0.05M XH2O = 55.5-0.05/55.5 = 0.9991 so pH2O from the beaker will be X*Ptotal and if we take a convenient number like 1 for Ptotal then pH2O = 0.9991 What about the 0.1M. XH2O = (55.5-0.1)/55.5 = 0.0082 The vapor ...
Friday, February 14, 2014 at 10:35pm

Chemistry
Is that Kp in bar? ........C3H8 ==> C3H6 + H2 Total P = 2 = pC3H6 + pH2 + pC3H8 Solve for pC3H8 = 2-p-p = 2-2p Kp = p*p/(2-2p) Solve for p = H2 = C3H6
Friday, February 14, 2014 at 9:57pm

Chemistry
This is not a simple question. 1. Use the Debye-Huckel relationship to calculate the pH of 0.01M HCl. That is not the simple pH = -log(0.01) = 2 2. Now do the same for the mixture of 0.01M HCl and 5.80g NaCl after converting NaCl to mols then to M. 3. Solve for delta pH.
Friday, February 14, 2014 at 9:15pm

Chemistry
(V1/T1) = (V2/T2) T must be in kelvin
Friday, February 14, 2014 at 9:07pm

chemistry
Use PV = nRT Remember T must be in kelvin for use in the formula, then must be converted back to C for the answer.
Friday, February 14, 2014 at 9:06pm

chemistry
A sample of gas has a volume of 1.30 L at STP. What is the temperature in °C if the volume is 13.0 L at 2.00 atm?
Friday, February 14, 2014 at 7:44pm

Chemistry
What is the final Celsius temperature if 4.42 L of nitric oxide gas at 35°C is cooled until the volume reaches 1.00 L? Assume the pressure remains constant.
Friday, February 14, 2014 at 7:44pm

Chemistry
1 atm = 10.1 Newtons/cm^2 to find that type 1 atm = Newtons/cm^2 into a Google search box 10.1 Newtons/cm^2 * 17.5*10^3 cm^2 = 177,000 Newtons use the Google search box again: 177000 newtons = pounds and you will get back 39,791 pounds
Friday, February 14, 2014 at 7:37pm

Chemistry
Steve gave you the combined gas law, but it seems that you were confused. The gas law is as followed: P1V1/T1=P2V2/T2 Where P1=75.0 cmHg V1=500.0 mL T1=273K +(-185ºC)=88K P2=55.0 cmHg V2=221.0mL and T2=? Solve for T2: T2=[T1*(P2V2)]/P1V1 T2=[88K*(55.0 cmHg*221.0mL)/(75.0 ...
Friday, February 14, 2014 at 7:14pm

Chemistry
If the surface area of a human body is 17,500 square centimeters, what is the total weight of the atmosphere on a human body expressed in pounds?
Friday, February 14, 2014 at 7:08pm

Chemistry
This answer is not correct
Friday, February 14, 2014 at 6:40pm

chemistry
C
Friday, February 14, 2014 at 6:36pm

Chemistry
PV/T remains constant, so (75.0)(500)/(-185+271) = (55)(221.0)/T T = 28°K Note that we don't really have to convert to L and Pa, because the same conversion factors would be applied to both sides of the equation. The only wrinkle is the °C-°K conversion, ...
Friday, February 14, 2014 at 6:31pm

Chemistry
A sample of oxygen gas occupies 500.0 mL at -185°C and 75.0 cmHg. Calculate the temperature in °C if the gas has a volume of 221.0 mL at a 55.0 cmHg.
Friday, February 14, 2014 at 6:10pm

Chemistry
A sample of gas has a volume of 1.30 L at STP. What is the temperature in °C if the volume is 13.0 L at 2.00 atm?
Friday, February 14, 2014 at 6:09pm

Chemistry
Chester makes 1L of a 0.01M HCl solution and measure the pH. Burt then adds 5.80 g of sodium chloride to Chester’s solution and measures the pH. Calculate the difference between the two pH values obtained.
Friday, February 14, 2014 at 6:05pm

chemistry
544
Friday, February 14, 2014 at 5:00pm

chemistry
Breaking the hydrogen bond between two water molecules is called dissociation
Friday, February 14, 2014 at 4:51pm

Chemistry
After finding the moles of H2, do the mole ratio between H2 and X in the equation. After that you have the grams of X and moles of X divide the grams by the moles and you will find the molar mass.
Friday, February 14, 2014 at 4:08pm

Chemistry
If the equilibrium constant K equals .05, and the reaction C3H8=C3H6 + H2 (all gases), starts with pure C3H8 and is allowed to reach equilibrium at 200 K at a total pressure of 2 bar. Calculate the partial pressure of H2 at equilbirum.
Friday, February 14, 2014 at 3:25pm

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